1. Field of the Invention
The present invention relates to a heat exchanger, for example a heat exchanger of laminate type or the like employed in a refrigeration cycle or the like of an automotive air-conditioning apparatus or the like.
2. Description of the Related Art
Generally, components forming a refrigeration cycle of an automotive air-conditioning apparatus are provided with a compressor, condenser, receiver, expansion valve, evaporator, and so on, and perform heat exchange with refrigerant of the evaporator and air in a passenger-compartment to cool a passenger compartment by circulating refrigerant in this sealed circuit. Accordingly, in this refrigeration cycle, refrigerant which has passed through the expansion valve becomes gas-liquid two phase and is introduced into the evaporator. In the evaporator, the refrigerant absorbs heat from external air and is vaporized (evaporated) thereat, continues isothermal expansion and performs a cooling effect for air in the passenger-compartment, and thereafter this expanded refrigerant becomes superheated vapor and is introduced into the compressor.
Additionally, in recent years a heat exchanger of laminate type has been developed from the standpoint of heat-exchanging performance and the like as a device utilized in the above-described refrigeration cycle. As shown in U.S. Pat. No. 5,245,843 (corresponding to Japanese Patent Application Laid-open No. 5-19632), the heat exchanger has a first and second heat-exchange portions. The first heat-exchange portion is formed by laminating thin plates which forms passages therein. The second heat-exchange portion is formed by laminating thin plates which forms passages therein and corrugated fins. The heat exchanger is provided with the first heat-exchange portion to heat exchange between the refrigerant of a refrigerant inlet path and the refrigerant of an outlet path, the second heat-exchange portion having a plurality of evaporation passages to heat exchange between the refrigerant and air in the compartment, and a fixed needle valve disposed between the refrigerant inlet path and the second heat-exchange portion, and so on. Accordingly, heat exchange between refrigerant and air in the compartment is performed by distributing and supplying refrigerant to the passages to the second heat-exchange portion via the needle valve, and along with this, mutual heat exchange between refrigerant is performed between refrigerants of different temperature to flow to the proximately arranged refrigerant inlet path and refrigerant outlet path in the first heat-exchange portion.
In producing the heat exchanger, comparing the constitution of the first heat-exchange portion and the second heat-exchange portion, the first heat-exchange portion is dense in material volume, and the second heat-exchange portion is coarse in material volume because corrugated fins are formed between thin plates. Therefore, when the heat exchanger having two parts of which density is different is brazed in a furnace, there is a problem. Setting the time and the temperature in the furnace to fit for the first heat-exchange portion which is dense (This means large thermal capacity.), fins in the second heat-exchange portion begins to melt when brazing of the first heat-exchange portion is completed. On the other hand, setting the time and the temperature in the furnace to fit for the second heat-exchange portion which is coarse (This means small thermal capacity.), the state of brazing in the first heat-exchange portion is incomplete when the brazing of the second heat-exchange portion is completed.